Are you using a blocking reagent that is free of biotin. Some blocking
reagents have free and/or endogenously biotinylated protein (milk and
BSA are probably the biggest potential offenders).
My suggestions: 1). try another blocking reagent and 2). you might
consider adding Tween20 (0.01%) in the diluent for the antibodies (don't
add in the blocking step!).
Keld
